Bags of corpses dug out of a mass grave found in northern Iraq on March 14, 2015.

Iraqi security forces have discovered at least 14 mass graves since the strategic city of Tikrit was liberated from the ISIL Takfiri terrorists last week.

According to an Iraqi security source, the mass graves contain the bodies of hundreds of Iraqi soldiers massacred by ISIL outside the northern city.

The victims were found in large pits in the grounds of former dictator Saddam Hussein’s presidential palaces on the banks of the Tigris River.

Most of the victims had their hands bound.

Kamel Amin, spokesman for Iraq’s Human Rights Ministry, said experts have started exhuming the remains of 47 people, adding that the number is expected to rise.

Ali Tahir, a morgue director supervising the exhumation, said the remains will be sent back to Baghdad for DNA tests to establish identify.

In June 2014, when ISIL seized Tikrit, the militants claimed they had killed 1,700 Iraqi soldiers who had surrendered at Speicher airbase outside the city.

They also published photos and videos showing militants shooting the soldiers. The Speicher massacre was one of the worst atrocities committed by the ISIL terrorists.

Human Rights Watch published aerial pictures last September, showing the alleged sites of the mass graves.

On March 31, Iraqi Prime Minister Haider al-Abadi said units of government forces, backed by Shia and Sunni volunteer forces, had managed to retake control of the city after heavy battles with ISIL.

The recapture of Tikrit is crucial for the Iraqi army in its quest to take control of the country’s second-largest city, Mosul.

Prime Minister Abadi recently said several people involved in the mass killing of soldiers have been detained.

ISIL started its campaign of terror in Iraq in early June 2014. The heavily-armed militants took control of Mosul before sweeping through parts of the country’s Sunni Arab heartland.

Over the past few months, Iraqi soldiers, police units, Kurdish forces, Shia volunteers and Sunni tribesmen have been engaged in battle to drive the terrorists out of the areas they have under control.